Circuit breaker truck position interlock



1959 c. R. GALLANT ETAL 2,916,571

cmcun BREAKER TRUCK POSITION INTERLOCK Filed Aug. 27, 1957 5 Sheets-Sheet 1 INVENTORS (A /7215s 641mm 1959 c. R. GALLANT ETAL 2,916,571

cmcun BREAKER TRUCK POSITION INTERLOCK Filed Aug. 27, 1957 5 Sheets-Sheet 2 1,, I I I I 1 I I 1 1 1 1 111 5 Sheets-Sheet 3 ICE-.5-

C. R. GALLANT EIAL CIRCUIT BREAKER TRUCK POSITION INTERLOCK Dec. 8, 1959 Filed Aug. 27, 1957 Dec. 8, 1959 c. R. GALLANT ETAL 2,916,571

CIRCUIT BREAKER TRUCK POSITION INTERLOCK Filed Aug. 27, 1957 5 Sheets-Sheet 4 BY WE/W dA/aselo W i W c. R. GALLANT rrm. 2,916,571

cmcun BREAKER TRUCK posmon INTERLOCK Filed Aug. 27, 1957 5 Sheets-Sheet 5 Dec. 8, 1959 I 1 W I r- INVENTORJ 69 221.65 6/1/04;

JTIVKW United States Patent C CIRCUIT BREAKER- TRUCK POSITION INTERLOCKv Charles R. Gallant, Beach-Haven Crest, N.J., and Joseph J; Onderko,.Philadelphia-, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporationof Pennsylvania.

Application August 27, 1957, Serial No..680,552

9 Claims. (Cl. 200-50) This. invention relates to an interlock mechanism for draw out circuit breakers for. selectively controlling movement of the circuit breaker. between the test andoperating positions, andv more specifically. relates toan interlockmechanism of the above type which is carried by the racking mechanism of the circuit breaker.

Truck mounted circuit breakers of the type to which our novel invention applies are fully set forth in copending application, SerialNo. 629,391, filed December 19, 1956, now Pat..No. 2,840,653, issued June 24, 1958,

which is herein made a part of. the instant application.

It is often required that truck mounted circuit breakers. of the above type. which may be racked between a test and operatingposition be. provided with an interlock means for preventing an accidental racking of a circuit.

breaker. from the test .to. the operating position.

In the past, this interlock. has been provided by a simple blocking device onthe floor guidesof the cubicle housing the circuit breaker, the blocking device being controlled by a rod which extends to the front of the.

cubicle. However, in the rack-in type of mechanism usually employed, a long lever is used for racking with.

an associated high mechanical advantage. Thus, the considerable force developed during the racking operationis sometimes suflicient to override the simple blocking device by either overriding the block or fracturing it. In somev cases where the block holds, severe damage is done to the breaker rack-in mechanism by the high forces which are developed.

The principle of our novel invention is to provide an interlock means within therack-in mechanism itself and at a point where the mechanicaladvantage of the mechanism from the operating lever to the interlock is relative- 1y-small. Furthermore,- the interlock device of our invention is constructed to prevent racking only from the test to the operating position, and loses control when the circuit breaker is in the operating position. Accordingly, the interlock mechanism cannot prevent racking from the operating position to the test position, and the.

dangerous condition of having the circuit breaker accidentally. locked in the operating position is avoided.

Accordingly, the primary object of our invention is to provide a novel interlock mechanism for truck mounted circuit breakers.

Another object of our inventionis to provide a novel interlock mechanism carried by the rack-in mechanism of'a-truck mounted circuit breaker which selectively prevents racking from the test position to the operating position and-is defeated when the circuit breaker is in the operating position.

Astillfurther object of our invention is to provide a novel interlock system which achieves interlocking within the racking mechanism and at a point where the mechanical advantage is relatively low.

Another. object of our'invention is to provide an interlock system which. is visually observable and can be secured by padlocking, key interlocks, or tagging.

These. andother. objects ofour invention will now be that our. novel interlock mechanism could be applied.

r 2,916,571 Patented. Dec. 8,, 1959..

the contacts of the circuit interrupting devices are inv their engaged position, and further shows the latching mechanism for latching the breaker in. its engaged posi: tion.

Figure 3 is in an exploded perspective view which specifically illustrates the racking mechanism, and shows. the manner in which it cooperates withthe slot means. fastened to the enclosure wall.

Figure 4 schematically illustrates-the racking mecha-. nism operation prior to entrance of the circuit controlling device to the cooperating. cubicle with: the side. wall of the cubicle removed.

Figure 5 is similar to Figure 4 and shows the rackingE mechanism immediately after entrance of the racking mechanism into the cubicle and prior to entrance to the. test position.

Figure 6 is similar to Figures 4 and 5 and showslthe racking. mechanism after racking from thetest position.

to the operating position.

Figure 7 illustrates our novel interlock mechanism in.

schematic form.

Figure 8' shows a top view of our. novel interlock.

be applied. It is to be understood, however, that Figure- 1 is set forth here for illustrative purposes only, and

to many types of enclosed switchgear devices.

The circuit breaker set forth in Figure 1.is specifically adapted for operation on voltages of the order of. 15;-

kilovolts and is generally comprised of an interphase barrier assembly 20 for isolation of adjacent phases, a.

front cover assembly 22, and a blowout structure 24.

Clearly, the blowout structure 24 cooperates with. anarc-chute 26 which serves to elongate and cool the. arc.

drawn between the stationary arcing contact 28 andthe movable. arcing contact 30 when the movable bridge.

assembly 32 is driven to a disengaged position so as.

to disengage the stationary main contact 34 and the movable main contact 36.

The device of Figure 1 further includes front. sup-- disengaged position against theforce of. the accelerating spring 58.

The main current path of the circuit interrupting. de vice shown in Figure 1 through the upper primary disconnect 48, stationary main contact 34, movable bridge assembly 32, the lower terminal 50, and the lower disconnect contact 52.

In order to rack the circuit breaker of Figure 1 between its test position, where the secondary disconnect contacts 60 are in engagement with cooperating second; ary contacts supported from the enclosure, andthe operating position, wherethe primary disconnect contacts and 52 are engaged with the cooperating disconnects supported from the enclosure'(not shown), a racking mechanism which is seen in Figure 1 as including the disk 62 and forms the essential portion of this disclosure is operatively connected through shaft 64 to an operating member 66 having a racking roller 68 attached at one end thereof.

As will be set forth more fully hereinafter, racking roller 68 engages a slot arrangement fastened to the cubicle well so that rotation of the shaft 64 by means of the racking disk 62 will move roller 68 Within a ver tical slot means in the enclosure well to thereby drive the complete circuit breaker equipment between predetermined positions within the cubicle.

As will be further set forth hereinafter, the closing arm assembly 70 of the operating mechanism 54 is mounted on rotatable shaft 72 which has an interference screw 74 protruding therefrom. This interference screw 74 provides a novel interlock means between the racking mechanism and the circuit breaker contacts wherein racking is prevented so long as the circuit breaker contacts are in their engaged position.

The operating mechanism 54 of Figure 1 is best seen in Figure 2 which shows the operating mechanism in its closed position rather than in the open position of Figure 1, and it is seen that the solenoid plunger 76 is moved to the right to drive the closing arm 70 and its shaft 72 in an anti-clockwise direction so as to drive movable bridge assembly 32 (Figure 1) to its engaged position. Closing arm 70 is maintained in its closed position by the prop-latch 78 and the trip-latch 80 which operates through the trip free linkage, including the linkages 32, and 86 as well as a linkage (not shown) which interconnects linkages 82 and 86. The trip-latch 80 which is mounted on the shaft 88 may have various trip mechanisms associated therewith for achieving instantaneous and time delayed trips, or manual trip actuated by manually operable means from the front of the panel. These mechanisms, however, have not been shown, since they are well known in the art.

Manual closing means are also provided by way of the closing socket 90 which can receive an operating rod and which cooperates with roller 92 of shaft 94 which has its other end operatively connected to the closing arm 70, whereby a clockwise rotation of manual closing means 90 about its pivot point 96' will effect the closing of the circuit breaker contacts.

The racking mechanism seen in Figure 1 as including racking disk 62, member 66 and roller 68 is best seen in the exploded perspective view of Figure 3.

Referring now to Figure 3, shaft 64 has the racking disk 62 rigidly fastened thereto by any desired means such as force-fitting, keying, or any other desired means so that the racking disk 62 will rotate with the shaft 64. Racking disk 62 has apertures such as the apertures 96, 98 and 100 of Figure 3 around its periphery which permit the entrance of a racking handle through an aperture of the lower front panel for the subsequent racking operation.

' Racking disk 62 is further provided with latch notches 106 and 108 which correspond to the operating and test positions respectively. Each end of the shaft 64 is then provided with extensions or members 110 and 112 respectively which are secured to the shaft in any desired manner, and have engaging means such as rollers 114 and 116 respectively mounted off the axis of shaft 64.

' As is best seen in Figure 3, the cubicle sidewalls 118 and 120 have cooperating engaging means such as the slot means 122 and 124 respectively fastened thereto in any desired manner, the slot means 122, by way of example, being formed of the two structural members 126 and 128 which are welded to the cubicle wall. These members are so positioned and formed with respect to one another that they will form a vertical channel 130 for receiving roller 114 when the breaker is moved into the cubicle.

The outer portion of member 126 is curved upwardly so as to receive roller 114 as it is moved into the cubicle and cam it down against the force of a biasing means, to be described hereinafter, so that when the roller 114 reaches the slot at a point which corresponds to the test position for the circuit breaker, the roller 114 will automatically move into the slot 130 and latch the breaker in the test position.

As is further seen in Figure 3, the U-shaped member 132 is positioned adjacent to racking disk 62 and has a downwardly bent tip 134 for receiving the tension spring 136 at one end thereof, the other end being fastened to a fixed portion of the structure 138.

More specifically, the U-shaped member 132 is rotatably mounted with respect to shaft 64 by means of the pin 140 which prevents the U-shaped structure from slipping off the shaft 64. Normal clockwise rotation of member 132 is prevented by means of the adjustment screw 142 which is threaded through a U-shaped member 132, and butts against stationary structural member 144.

As will be more apparent hereinafter, when the racking disk 62 is initially rotated in a counter-clockwise direction or in a direction opposite to the direction of angular rotation for racking from the test to the operating position, the projection 149 will pick up the extended arm of member 132 to cause this member to rotate with the racking disk and extend the spring 136. This occurs as the circuit breaker is inserted within the cubicle and the roller 114 is cammed down by the upwardly extending cammed surface of member 126, and the condition is specifically shown in the Figure 6 wherein the shaft 64 has been rotated in a counter-clockwise direction, and spring 136 extended to bias the shaft 64 in a clockwise direction.

Thus, when the entire mechanism is moved so that the roller 114 approaches the channel 130, the engagement between roller 114 and the under surface of member 126 will prevent clockwise rotation of shaft 64 by the spring 136. When, however, roller 114 reaches the channel 130, the spring 136 will move the roller 114 upwardly by rotating shaft 64 through the member 132, member 149 and racking disk 62.

Accordingly, the racking mechanism operates to latch the circuit breaker in test position when it is initially moved into the cubicle.

As has been described hereinbefore, the racking disk 62 is provided with latching notches 106 and 108. These racking notches cooperate with a latch member 146 which is fastened in any desired manner to the racking release arm 148. Racking release arm 148 is pivotally mounted at pivot point 150, as seen in Figure 3, and its right-hand end has a U-shaped operating member 152 which is operable through an aperture in the lower front panel of the circuit breaker. The left-hand portion 154 of racking release lever 148 is then positioned adjacent to the interference screw 74 of the closing arm shaft 72 so that rotation of racking release lever 148 in a clockwise direction about its pivot point 150, will be prevented by the interference screw 74, so long as the shaft 72 is in a position which corresponds to contact engagement.

When the contacts are in a disengaged position, however, shaft 72 will rotate to the position shown in dotted lines in Figure 3, whereby the racking release lever may be rotated in a clockwise direction to remove the latch 146 from either of the latch notches 106 or 108.

If desired, operation of the racking release lever 148 could be coordinated with the trip latch 80 (Figure 2) of the circuit breaker, whereby, prior to engagement of the interference screw 74, the circuit breaker will be automatically tripped to its disengaged position so as prevent damage to the racking release lever by a forceful engagement with the interference screw 74.

This structure is set forth in Figure 3, and is comprised of a member 156 which is fastened to the racking release lever 148 and is movable therewith and is movable 5. intoengagernent with a trip arm '158 which is pivotally mounted at pivot point 160, and biased in a counterclockwise direction by the tension spring 162.

The left-hand edge of the trip arm 158 is positioned adjacent an extension of the trip latch 80 so that an attempted depression of the racking release arm 148 will cause rotation of trip arm 158 and its pivot point 160 in a clockwise direction, and the left-hand end of the trip arm will rotate trip latch 80 in a counter-clockwise direction about its shaft 88 to trip the breaker.

Further depression of the racking release arm 148 is then permissible, since the interference screw 74 is in its dotted position, as soon in Figure 3, in view of the disengaged contacts.

. Figures 4, and 6 schematically illustrate portions of the racking mechanism described in conjunction with Figure 3, and are particularly well adapted in describing the operation thereof.

.In Figures 4, 5 and 6 a circuit breaker, which could be of the type set forth in Figure 1, is seen to be movable into and out of engagement with the enclosure having the side wall 118 (see Figure 3) and a front panel 170. Each ofIFigures 4, 5 and 6 further show the slot means 122 of the wall 118 as including the members 126 and 128 of Figure 3 for defining the slot 130.

It is tobe noted that the complete cubicle is not shown in Figures 4, 5 and 6, and it will be readily understood by-those skilled in the art that the rear of the cubicle will. be adapted with primary disconnect contacts which cooperatewith the disconnects 48 and 50 of the circuit breaker, and will similarly have contacts for cooperating withthe secondary contacts (see Figure 1) carried by the'circuit breaker. Furthermore, the interlocking linkage between the racking disk 62, the racking release lever 148 and trip latch 80 are shown in Figures 4, 5 and 6 in a schematic form for the sake of simplicity, but, nevertheless, operate in a manner identical with that set forth for the structure in Figure 3.

The operation of the racking mechanism proceeds as follows:

'-When the circuit breaker is completely removed from the enclosure as seen in Figure 4, the racking mechanism willbe in the position'shown in Figure 3. As the circuit' breaker is Wheeled into the cubicle, as seen in Figure 5, the roller 114 will engage the cam plate 172 of member 126 so as to cause rotation of shaft 64 in a counterclockwise direction. In view of this counter-clockwise rotation, spring 136 (Figure 3) will be extended. In moving to this position, the latch 146 will be cammed downwardly 'by means of the sloped notch 108 so as to cause the racking release lever to rotate about its pivot point 150 (Figure 3) and thereby assure that the circuit breaker is tripped in view of the interconnection between the racking release lever 148 and the trip latch 80.

It is to be noted, however, that if this interconnection were not present and the circuit breaker contacts were closed, that the camming action of the latch 146 would not be possible when the roller 114 (as well as the roller 116 which would cooperate in an identical manner with a slot in the other wall of the cubicle) engages the cammed plate 172 of member 126, since the interference screw 74 would not permit rotation of the racking release lever 148. Accordingly, operating personnel would realize that the circuit breaker contacts are engaged, and would then be able to trip the circuit breaker prior to movement to the test position.

The circuit breaker is then moved into the cubicle as seen in Figure 5, until the roller reaches the stop plate 128, and the extended spring 136 drives the racking disk shaft 64 in a clockwise direction, in view of the connection from the biasing spring 136 to the U-shaped member'132 and the pin 149 of racking disk 62, so that the roller 114 will be moved to the dotted position seen in 6 Figure 5, and the breaker will be latched in the test position. That is to say, it will not be possible now to move the breaker from the test position without using the racking handle 174 to rotate the racking disk 64 in such a direction as to bring the roller 114 out of the slot 130.

If it is now desired to move the circuit breaker from the test position to a position outside of the cubicle, the racking handle 174 is inserted in one of the holes in the racking disk such as the hole of Figure 3, and the racking disk is moved upwardly to move the roller 114 downward and out of slot 130, and the circuit breaker may be thereafter pulled out of the cubicle.

When moving from the test position (shown by the dotted view of roller 114 of Figure 5 to the operating position of Figure 6), the racking release arm is depressed by manually depressing member 152. Thus, when the circuit breaker contacts are in their engaged position, the engagement between extension 156 and trip bar 158 will cause operation of the trip latch 80 to trip the breaker and prevent interference between extension 154 of racking release arm 148 and interference screw 74. If there is no interconnection between the trip latch 80 and the racking release arm 148, then the disengagement of latch 146 from notch 108 will be defeated in view of the interference screw 74, and the operator will have to physically trip the breaker from a manual trip means before racking to the operating position.

The racking handle 174 may then be inserted into an appropriate racking hole, and the racking disk 62 and the shaft 64 are rotated in a clockwise direction. In view of this rotation, the racking roller 114 will move upward in the slot and the circuit breaker will be moved inwardly.

It is to be noted that when rotating the racking shaft 64 in a clockwise direction, that the projection 149 of Figure 3 is moved away from the U-shaped member 132 and that this member does not interfere with the racking operation from test to operating position.

Thus, the handle is operated, removed and reinserted into the next appearing holes in the racking disk 62 until the circuit breaker is positioned in its operating position within the cubicle, as seen in Figure 6, and the primary disconnect contacts 48 and 50 are in engagement with cooperating primary disconnect contacts supported from the cubicle.

Note that when the circuit breaker achieves the operating position, the latch notch 106 (Figure 3) moves into engagement with latch 146 of racking release arm 148, and the racking disk 62 and racking shaft 64 are latched in this position.

Therefore, in order to rack the circuit breaker from the operating position of Figure 6 to the test position of Figure 5, it is once again necessary to depress member 152 of racking release arm 148 and defeat the latch engagement between notch 106 and latch 146. Here again, however, the circuit breaker contacts must be disengaged in view of the interference screw "/4.

Thus, the mechanism is provided with the automatic linkage between the racking release lever 148 and trip latch 80, the breaker will be automatically tripped on operation of the racking release lever 148. If, however, this linkage is not present it will be impossible to press racking release latch 148, and circuit breaker will have to be manually tripped.

Once the latch engagement between notch 108 and latch 146 has been defeated, the operator inserts the racking handle 174 in an exposed notch in the racking disk 62 and rotates racking disk 62 and its shaft 64- in a counterclockwise direction to cause roller 114 to move upwardly in the slot 130, and move the circuit breaker to the test position of Figure 5, as seen by the dotted position of roller 114.

In the foregoing, it is .seen that racking between the test and operating positions may be accomplished only with the circuit breaker contacts in their disengaged position by virtue of the interference screw 74 and racking disk latch. Thus, the racking mechanism provides an extremely simple interlock structure which may be operated with relatively little force and in a relatively quick time.

Furthermore, this racking mechanism provides the extremely desirable advantages of automatically latching the circuit breaker in its test position when it is moved into the cubicle.

The essence of our novel interlock mechanism is set forth in Figures 7, 8 and 9 in conjunction with the device described above with reference to Figures 1 through 6.

Referring now to Figures 7, 8 and 9, it is seen that a U-shaped bracket 200 is fastened in any desired manner to the horizontal portion of runner 126 while a block 202 having an aperture therein is fastened to the vertical portion of runner 126 in any described manner. The aperture in block 202 slidably receives a bolt 204 which, as will be seen hereinafter, is the locking member of the interlock mechanism.

Bolt 204 is axially moved within the aperture in block 202 by a linkage including members 206 and 208 which are supported from the U-shaped member 200. More specifically, member 206 is slidably supported by member 200 by means of pins 210 and 212 fastened to member 200 which engage slots 214 and 216 respectively of memher 206 while member 208 is pivotally mounted to U-shaped member 200 by means of the pin 218.

One end of L-shaped member 208 is pivotally connected to a flattened end portion of bolt 204 by means of pin 208 which passes through slot 222 of member 202 while the end of the other leg of L-shaped member 208 is pivotally connected to the left hand end of memher 206 by means of pin 224 which passes through slot 226 in member 208 and pin 224 is then terminated in member 206.

In view of the above described mechanism, it is seen that by withdrawing member 206 by pulling its handle 230 outwardly, that the bolt 204 will be moved out or downwardly in Figure 8. Conversely, by pushing mem ber 206 inwardly, the bolt 204 will be withdrawn.

Members 200 and 206 are further provided with apertures 227 and 299, which, as will be seen hereinafter, may operate to lock the interlock mechanism with the bolt 204 in its extended position.

The interlock mechanism of Figures 7, 8 and 9 is completed by the plate 232 which is rigidly fastened to arm 110 and is concentrically positioned with respect to roller 114. Plate 232, as best seen in Figures 7 and 9, is preferably constructed with a depression 234 which can move into cooperating engagement with respect to bolt 204.

In operation, the operating handle 230 of member 206 may be extended as far as desired, or may be remotely operated in any desired manner. When the arm 110 is in the phantom position shown in Figure 9, which is the test position, and it is desired to prevent the circuit breaker from being racked to the operating position, it is only necessary to move the member 206 to the right with respect to Figure 8. This will cause member 208 to rotate in a counter-clockwise direction to thereby drive the bolt 204 outwardly (to the dotted line position shown for the end of the bolt 204 in Figure 8) and to a position where the depression 234 of plate 232 will engage the bolt 204 if the arm 110 is cranked toward the operating position.

In order to further insure defeat of the racking mech anism with the breaker in the test position, a padlock or tag may be passed through apertures 227 and 299, or a key interlock (not shown), can pass its bolt through these apertures.

Thus, our novel invention provides a novel means for preventing movement of the breaker to the operating position unless the member 206 is depressed. It is to be noted that the interlock mechanism is so constructed as to achieve locking at a point where the mechanical advantage for racking is small. Therefore, a relatively simple mechanism will prevent operation of the racking mechanism even though considerable force is used.

Furthermore, the interlock mechanism cannot be operated when the circuit breaker is in the operating position to thereby accidentally lock the breaker in this position. That is, when the breaker moves to the operating position, a portion of disk 232; of Figures 7, 8 and 9 moves into registry with bolt 204, and bolt 204 cannot be extended into a locking position.

A further advantage presented is that the handle 230 can be extended to the front panel of the cubicle where it may offer a visual indication of the interlock position.

Although we have here described preferred embodiments of our novel invention, many variations and modifications will now be apparent to those skilled in the art, and we prefer therefore to be limited not by the specific disclosure herein but only by the appended claims.

We claim:

1. An interlock mechanism for truck mounted circuit breakers having racking mechanism for racking said circuit breaker between a test position and an operating position, said racking mechanism comprising a first mechanism carried by said circuit breaker and a second mechanism adapted to cooperate with said first mechanism during racking operation, said second mechanism being supported relatively stationary with respect to said circuit breaker; said interlock mechanism being operatively con nected to at least one of first or second mechanisms; said interlock mechanism being selectively operable to defeat said cooperation between said first and second mechanisms when said circuit breaker is in said test position to thereby defeat racking from said test position to said operating position.

2. An interlock mechanism for truck mounted circuit breakers having racking mechanism for racking said circuit breaker between a test position and an operating position, said racking mechanism comprising a first mechanism carried by said circuit breaker and a second mechanism adapted to cooperate With said first mechanism during racking operation, said second mechanism being supported relatively stationary with respect to said circuit breaker; said interlock mechanism being operatively connected to at least one of first or second mechanisms; said interlock mechanism being selectively operable to defeat said cooperation between said first and second mechanisms when said circuit breaker is in said test position to thereby defeat racking from said test position to said operating position, said interlock mechanism being defeated when said circuit breaker is in said operating position.

3. An interlock mechanism for truck mounted circuit breakers having racking mechanism for racking said circuit breaker between a test position and an operating position, said racking mechanism comprising a first mech anism carried by said circuit breaker and a second mechanism adapted to cooperate with said first mechanism during racking operation, said second mechanism being supported relatively stationary with respect to said circuit breaker; said interlock mechanism being operatively connected to at least one of first or second mechanisms; said interlock mechanism being selectively operable to defeat said cooperation between said first and second mechanisms when said circuit breaker is in said test position to thereby defeat racking from said test position to said operating position, said first mechanism comprising an extending member rotated by racking operation, said second mechanism comprising a channel adapted to receive said extending member; said interlock mechanism comprising a plate carried by said extending member and a means positionable for interfering with the motion of said extending member when said circuit breaker is racked from said test to said operating position.

4. An interlock meqhaui for truck mounted circuit breakers having racking mechanism for racking said circuit breaker :between a test position and an operating position, said racking mechanism comprising a first mechcarried by said circuit breaker and a second mechanism adapted to cooperate with said first mechanism during racking operation, said second mechanism being supported relatively stationary with respect to said circuit breaker; said interlock mechanism being operatively connected to at least one of first or second mechanisms; said interlock mechanism being selectively operable to defeat said cooperation between said first and second mechanisms when said circuit breaker is in said test position to thereby defeat racking from said test position to said operating position, said first mechanism comprising an extending member rotated by racking operation, said second mechanism comprising a channel adapted to receive said extending member; said interlock mechanism comprising a plate carried by said extending arm and a means positionable for interfering with the motion of said extending arm when said circuit breaker is racked from said test to said operating position; said plate being further constructed to prevent the positioning of said interfering means in an interfering position when said circuit breaker is in said operating position.

5. An interlock mechanism for truck mounted circuit breakers having racking mechanism for racking said circuit breaker between a test position and an operating position, said racking mechanism comprising a first mechanism carried by said circuit breaker and a second mechanism adapted to cooperate with said first mechanism during racking operation, said second mechanism being supported relatively stationary with respect to said circuit breaker; said interlock mechanism being operatively connected to at least one of first or second mechanisms; said interlock mechanism being selectively operable to defeat said cooperation between said first and second mechanisms when said circuit breaker is in said test position to thereby defeat, racking from said test position tosaid operating position, said interlock mechanism being defeated when said circuit breaker is in said operating position; the position of said interlock mechanism being visually observable.

6. An interlock mechanism for truck mounted circuit breakers having racking mechanism for racking said circuit breaker between a test position and an operation position, said racking mechanism comprising a first mechanism carried by said circuit breaker and a second mechanism adapted to cooperate with said first mechanism during racking operation, said second mechanism being supported relatively stationary with respect to said circuit breaker; said interlock mechanism being operatively connected to at least one of first or second mechanisms; said interlock mechanism being selectively operable to defeat said cooperation between said first and second mechanisms when said circuit breaker is in said test position to thereby defeat racking from said test position to said operating position; and locking means associated with said interlock mechanism, said locking means being adapted to lock said interlock mechanism in an interlock position when said circuit breaker is in said test position.

7. In a circuit controlling device movable between a test and operating position within a cubicle, said circuit controlling device having a pair of cooperable contacts movable between an engaged and a disengaged position, a racking mechanism fastened to said circuit controlling device for racking said circuit controlling device between said test and operating positions; said racking mechanism comprising a racking disk operatively connectable to a portion of said cubicle to move said circuit controlling and outpf latchingengagement with respect to said racking ,disk when said circuit controlling device is in said test and said operating positions for preventing and allowing respectively operation of said racking disk; infifel'euce ,means movable responsive to movement .of one of said pair of cooperable contacts, said interference means being positioned .to prevent movement of said racking disk latch means out of latching engagement with respect to said racking disk when said pair of cooperable contacts are in said engaged position, said interference means being positioned to allow movement of said racking disk latch means out of said latching engagement with respect to said racking disk when said pair of cooperable contacts are in said disengaged position; and interlock means associated with said racking mechanism for selectively defeating rotation of said racking disk for racking said circuit controlling device from said test position to said operating position.

8. In a circuit controlling device movable between a test and operating position within a cubicle, said circuit controlling device having a pair of cooperable contacts movable between an engaged and a disengaged position, a racking mechanism fastened to said circuit controlling device for racking said circuit controlling device between said test and operating positions; said racking mechanism comprising a racking disk operatively connectable to a portion of said cubicle to move said circuit controlling device with respect to said cubicle responsive to operation of said racking disk, and a racking disk latch means; said racking disk latch means being movable into and out of latching engagement with respect to said racking disk when said circuit controlling device is in said test and said operating positions for preventing and allowing respectively operation of said racking disk; interference means movable responsive to movement of one of said pair of cooperable contacts, said interference means being positioned to prevent movement of said racking disk latch means out of latching engagement with respect to said racking disk when said pair of cooperable contacts are in said engaged position, said interference means being positioned to allow movement of said racking disk latch means out of said latching engagement with respect to said racking disk when said pair of cooperable contacts are in said disengaged position; and interlock means associated with said racking mechanism for selectively defeating rotation of said racking disk for racking said circuit controlling device from said test position to said operating position; said interlock mechanism being defeated when said circuit breaker is in said operating position.

9. In a circuit controlling device movable between a test and operating position within a cubicle, said circuit controlling device having a pair of cooperable contacts movable between an engaged and a disengaged position, a racking mechanism fastened to said circuit controlling device for racking said circuit controlling device between said test and operating positions; said racking mechanism comprising a racking disk operatively connectable to a portion of said cubicle to move said circuit controlling device with respect to said cubicle responsive to operation of said racking disk, and a racking disk latch means; said racking disk latch means being movable into and out of latching engagement with respect to said racking disk when said circuit controlling device is in said test and said operating positions for preventing and allowing respectively operation of said racking disk; interference means movable responsive to movement of one of said pair of cooperable contacts, said interference means being positioned to prevent movement of said racking disk latch means out of latching engagement with respect to said racking disk when said pair of cooperable contacts are in said engaged position, said interference means being positioned to allow movement of said racking disk latch means out of said latching en- I References Cited in the file of this patent I I UNITED STATES PATENTS Hebbel Mar. 6, 1951 Hawkins et a1. Oct. 16, 1956' Frink et al. May 14, 1957 

